The present invention relates to a helical gear grinding machine, and more particularly to a helical gear grinding machine for grinding helical gear teeth with a grinding wheel having helical grooves defined in a peripheral edge thereof such that the helical gear will be displaced with respect to the grinding wheel under automatic control for grinding the helical gear teeth properly dependent on their respective helix angles.
For grinding a gear across the entire face width, it is necessary to displace the gear in an axial direction thereof. Where a helical gear having twisted gear teeth is to be ground, the condition of synchronous rotation of a grinding wheel and the gear dependent on their gear ratio has to be changed to the extent commensurate with the axial displacement of the gear. Furthermore, the teeth of the helical gear are ground with poor accuracy since central and opposite end portions of the teeth in the direction of the face width are subjected to grinding resistances from the grinding wheel which differ in magnitude and direction. In addition, the gear grinding machine suffers from errors in the accuracy with which to grind the gear teeth. To eliminate these accuracy defficiencies, the condition of synchronous rotation of the grinding wheel and the gear ground thereby is also required to be changed.
Conventional helical gear grinding machines include a differential gear and a train of speed reduction gears through which a helical gear being ground is rotated by a workpiece drive motor, the differential gear having a gear ratio variably dependent on the extent and direction of displacement of the helical gear. Such a prior grinding machine arrangement has however had many disadvantages. For example, it requires many precision differential gears so as to be able to grind helical gears of different helix angles. Where the differential gear is to be replaced for a different gear ratio, the replacement procedure is tedious and time-consuming, resulting in a prolonged downtime of the grinding machine. The prior helical gear grinding machine has also been disadvantageous in that its accuracy of operation is lowered because of many gears interposed between the workpiece drive motor and the helical gear being ground, and the synchronizing rigidity is reduced.